1. Field of the Invention
The present invention relates generally to birdhouses and similarly configured feeders, and more specifically, to the convenient repeated depth adjustment capability of a false floor by means permanently containable within such structures to allow variation in depth settings for feeding, encouraging and protecting nestings of desirable birds, and discouraging nestings of undesirable birds.
2. Description of Prior Art
Various beneficial and desirable native birds, such as bluebirds and chickadees benefit from artificial nesting and feeding structures (bird houses and similarly constructed feeders; a bird house may also be considered a bird feeder if bird feed is placed inside an unoccupied nesting box and may be referred to as a birdhouse, birdbox, nesting box, feeding box, nesting/feeding box, or box. These structures are most beneficial with human management such as removal of old nests, undesirable birds' nests, parasites, etc. These structures are often, though not necessarily, built with four side wall panels, preferably with one side wall panel hinged or removable to permit access for human management. These structures are traditionally built with the floor at a permanently fixed depth below the bird entry hole. This fixed depth does not suit the varying biological conditions and purposes of these nesting/feeding boxes.
Predators such as raccoons and cats insert paws and forelegs through the bird entry holes of birdhouses, reaching down to seize nests, eggs, nestlings or incubating adults. Birdhouses built with greater fixed depth from bird entry hole to fixed floor may afford greater protection from this sort of predation, however some desirable birds demonstrate an aversion to nest in these deeper boxes. Those birds which do accept deeper boxes often negate the protective intent of the deeper box by filling the extra depth with additional nesting material, thus raising the egg cup at the top of the nest to a level dangerously close to the bird entry hole after all.
These deeper, built up nests are also unhealthy for desirable birds, as once dampened by driven rain, the nest will remain damp and cold longer, and harbor more blood sucking avian parasite blowfly larvae than will shallow nests. Some desirable birds such as bluebirds will cease nest building once the first egg is laid, and will then tolerate the lowering of the nest to a safer level. Wildlife managers sometimes lower the nest cup by inserting the fingers between the upper nest cup and the excess material of the lower portion of the nest, and removing the latter. This undermining may, however, disrupt the interwoven structure of the upper nest cup, and spillage of any removed material may attract predators by scent. This method is inconvenient, unsanitary, and exposes the hands to various pests which may inhabit the nest, such as mice, fleas, and ticks. For these reasons this method of lowering a nest is inferior to that permitted by the present invention.
Desirable native birds compete with undesirable destructive alien birds, such as English sparrows, for use of nesting boxes. English sparrows destroy nests, eggs, nestlings and incubating adults of native species while usurping nesting boxes intended for the latter. Ongoing field research suggests that while some desirable native birds such as bluebirds may prefer shallow nesting boxes, the undesirable English sparrow may have an aversion to shallow boxes.
A prior art device to vary the depth of bluebird houses to discourage nesting by English sparrows has been described in Sialia, the quarterly journal of the North American Bluebird Society in Volume 6, Number 1, pages 5-7, (Winter 1984). The device simply consists of one or more wood blocks placed or stacked on the fixed floor inside a birdhouse, prior to nest building, creating a shallow box less attractive to English sparrows but acceptable to bluebirds. The blocks may also be removed later to protectively lower the nest of desirable birds that build a shallow nest atop the blocks.
Just as some desirable birds are reluctant to enter a deep box to nest, some are reluctant to enter a deep box to feed, or are initially unable to discover feed placed low on the fixed floor of a deep box, away from the illumination of the bird entry hole.
A prior art device to lessen the depth of a bluebird nesting box, thereby adapting the box for use as a feeder, has been described in Bluebird News, a monthly wildlife management newsletter, on page 5 of the August 1989 issue. A small container, or wood blocks, are placed on the fixed floor inside a birdhouse. A feed tray is placed atop the container or blocks to hold bird feed closer to the bird entry hole, where it is more likely to be discovered by desirable birds. The description mentions that it may be necessary to lower the feed tray thereafter, if undesirable birds or animals too large to enter the feeding box attempt to reach the feed within.
These prior art depth adjustment devices, whether they be a container, other object, or one or more wood blocks simply placed on, or removed from, the fixed floor inside a nesting/feeding box, are inconvenient to use. These objects must be carried to or from the nesting/feeding box to effect a box depth adjustment, and must be handled and stored elsewhere when not in use in the box. This is especially inconvenient and unsanitary for those wildlife managers who maintain several, even hundreds, of boxes, often far afield. Also; removal of depth adjusting objects from a box may result in spillage of fine debris, creating a scent trail for predators leading back to the box. For these reasons prior art depth adjustment devices are inferior to the present invention.
As mentioned above, bird nests may become damp and often harbor the blood sucking parasitic larvae of the blowfly. Either condition is unhealthy for nestlings and may cause death.
A prior art device, described in Sialia, Volume 6, Number 2, page 70 (Spring, 1984), has been found to control both problems to some extent. This device is formed from a rectangle of hardware cloth (wire mesh) by making two right angle bends parallel to the two opposite short sides. This formed channel is inverted and stood on its legs which rest on the fixed floor of a birdhouse. (This elevated wire platform may be considered to be a form of false floor, though not intended for box depth adjustment. Some wildlife managers place a square of cardboard on this wire platform, hiding the unnatural looking wire until the nest building is complete.) The nest is built or retroactively placed on the wire platform. Rainwater which penetrates the nestbox will drain through the wire platform to the fixed floor, and out of the bottom of the box through drain holes drilled in or cut from the corners of the fixed floor. The airspace below the wire platform isolates the bottom of the nest from the damp fixed floor, and ventilates the underside of the nest and fixed floor, by permitting flow of air through the drainage holes. The drier nest is warmer for young nestlings and less hospitable to parasitic blowfly larvae. Also, larvae which fall through this wire mesh trap have some difficulty climbing back up to the nest. However, the legs of the wire platform may serve as a ladder, enabling some parasites to climb back up to the nest. The legs interfere somewhat with the free flow of water and air through drain holes cut from the corners of the fixed floor, limiting the beneficial drainage and ventilation effect. The legs also interfere with efforts to clean the surface below to remove trapped parasites and debris, unless the wire platform and nest are lifted. This prior art wire platform, dependent on legs bearing on the fixed floor for support, is inferior to the wire mesh or perforated platform support configuration permitted by the present invention.